This invention relates generally to golf club apparatus, and more particularly to a shaft for a golf club which is lightweight but can provide the necessary stiffness characteristics demanded by golfers.
Ideally, a golf shaft should be designed such that the outer diameter thereof is smoothly tapered by reducing the diameter from a grip end to a tip or hosel end by means of a swaging operation. This swaging would achieve the reduced diametrical dimensions along the circumferential axis of the shaft without introducing abrupt diameter reductions while at the same time maintaining a gradual wall thickness increase from the grip end to the tip. It has been found, however, that the manufacturing expense of such a golf shaft processed by the above noted swaging method is prohibitive and that the final appearance of the golf shaft is less pleasing than other types of configurations.
Moreover, it is generally known that an ideal golf shaft should be of negligible weight while at the same time providing sufficient stiffness characteristics to allow effectively all of the kinetic energy developed by the golfer to be transmitted to the golf ball with a high degree of control over the resulting shot. However, in practice, it is not possible to manufacture an effective club shaft having negligible weight; therefore, the design of conventional club shafts varies substantially from the ideal.
Conventional present day golf shafts typically achieve the reduction in diameter from the grip end to the tip by means of a series of step portions disposed along the length of the shaft, with the diameters of the step portions becoming progressively smaller toward the tip end. Adjacent step portions are separated by narrow transitional portions which comprise an abrupt reduction of diameter from one step to an adjacent step. It has been found, however, that the use of these abrupt transitional portions results in undesirable characteristics for the golf shaft. These undesirable characteristics include: (a) the establishment of stress concentration points along the circumferential axis of the shaft at the abrupt transitional portions; (b) the assumption of a relatively disjointed line of dynamic deflection of the shaft during swinging of the club; and (c) the club shaft must be of relatively heavy weight to overcome the disadvantages (a)-(b) noted above.
One successful attempt at reducing the weight of a golf shaft is shown and described in Kaugars U.S. Pat. No. 4,169,595, assigned to the assignee of the instant application. The club shaft disclosed in that patent utilizes a series of steps of varying lengths disposed along the length of the shaft wherein the particular configuration of steps results in a stronger shaft. This increase in strength permits the average wall thickness of the shaft to be reduced, in turn leading to a reduction of weight with the attendant advantages noted above.